In the manufacture of concrete manhole sections it is necessary to provide steps in the walls of the sections to enable workmen to descend and ascend the manhole when the same has been installed in the ground. Steps of U-shaped configuration have become popular. Heretofore various methods have been utilized to fix such steps in the manhole sections. The most prevalent of the prior art methods has been for a workman to enter the green manhole section and drive the steps into place by hammering the steps into the wall of the section using a sledge. According to another method the steps are urged into the green concrete while vibrating them.
A number of disadvantages attend the prior art methods of step installation, not the least of which is the time-consuming labor of the installations. According to any of such methods it has been necessary to have a workman enter the manhole section to carry out the installation. This involves providing some means to enable him to climb up and then descend into the section. Also, none of the prior art methods provide a rapid and at the same time reliable installation.
Considering the fact that the steps in an installed manhole are often in a very damp atmosphere, and that the manhole sections may have been installed for many years in the ground before it is necessary for a workman to descend into the manhole, it is important from a safety standpoint that the steps continue to have a reliable mounting in the manhole wall and that the mounting be such as to discourage corrosion of the steps at their points of anchor in the wall.
In addition, when the steps are hammered or vibrated into place the severe pounding and vibrations necessary to effect the penetration of the step into the manhole wall tend to disturb the green concrete and cause settlement thereof and consequently adversely affect the reliability of the manhole wall itself. Also, when the step is hammered in place by a workman, there is a problem of insuring that the step has been driven into the wall far enough to effect a long-life anchor and yet has not been driven so far through the wall as to give rise to infiltration of surrounding water which, if the same occurs, could lead to early failure of the step installation if not the manhole section itself.